Carbon nanotubes are known to have extraordinary tensile strength, including high strain to failure and relatively high tensile modulus. Carbon nanotubes may also be highly resistant to fatigue, radiation damage, and heat. To this end, the addition of carbon nanotubes to composite materials can increase tensile strength and stiffness of the composite materials.
Within the last fifteen (15) years, as the properties of carbon nanotubes have been better understood, interests in carbon nanotubes have greatly increased within and outside of the research community. One key to making use of these properties is the synthesis of nanotubes in sufficient quantities for them to be broadly deployed. For example, large quantities of carbon nanotubes may be needed if they are to be used as high strength components of composites in macroscale structures (i.e., structures having dimensions greater than 1 cm.)
One common route to nanotube synthesis can be through the use of gas phase pyrolysis, such as that employed in connection with chemical vapor deposition. In this process, a nanotube may be formed from the surface of a catalytic nanoparticle. Specifically, the catalytic nanoparticle may be exposed to a gas mixture containing carbon compounds serving as feedstock for the generation of a nanotube from the surface of the nanoparticle.
Recently, one promising route to high-volume nanotube production has been to employ a chemical vapor deposition system that grows nanotubes from catalyst particles that “float” in the reaction gas. Such a system typically runs a mixture of reaction gases through a heated chamber within which the nanotubes may be generated from nanoparticles that have precipitated from the reaction gas. Numerous other variations may be possible, including ones where the catalyst particles may be pre-supplied.
In cases where large volumes of carbon nanotubes may be generated, however, the nanotubes may attach to the walls of a reaction chamber, resulting in the blockage of nanomaterials from exiting the chamber. Furthermore, these blockages may induce a pressure buildup in the reaction chamber, which can result in the modification of the overall reaction kinetics. A modification of the kinetics can lead to a reduction in the uniformity of the material produced.
An additional concern with nanomaterials may be that they need to be handled and processed without generating large quantities of airborne particulates, since the hazards associated with nanoscale materials are not yet well understood.
The processing of nanotubes or nanoscale materials for macroscale applications has steadily increased in recent years. The use of nanoscale materials in textile fibers and related materials has also been increasing. In the textile art, fibers that are of fixed length and that have been processed in a large mass may be referred to as staple fibers. Technology for handling staple fibers, such as flax, wool, and cotton has long been established. To make use of staple fibers in fabrics or other structural elements, the staple fibers may first be formed into bulk structures such as yarns, tows, or sheets, which then can be processed into the appropriate materials.
Long nanotubes, which may have dimensions of 20 nm or less in diameter and 10 microns or more in length, can have relatively high aspect ratios. These nanotube fibers, when produced in large quantities from, for instance, chemical vapor deposition, may be used as a new source of staple fibers despite being smaller than most other textile staple fibers.
Accordingly, it would be desirable to provide a system and an approach to collect and handle synthesized nanotubes that can minimize the generation air-borne particulates, and in such a way as to permit processing of the nanotubes into a fibrous material of high strength for subsequent incorporation into various applications, structural or otherwise.